How are calories measured?
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** What are calories? How are they measured in food? **
Please copy/paste the following text to properly cite this HowStuffWorks
"What are calories? How are they measured in food?" 02 July 2001.
*Food & Nutrition*
· How Dieting Works
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· How many calories does a person need daily?
A *calorie* is a unit of energy. We tend to associate calories with food,
but they apply to anything containing energy. For example, a gallon (about
4 liters) of gasoline contains about 31,000,000 calories. You could drive a
car 22 miles (35 km) on the calories in 217 Big Macs.
Specifically, a calorie is the amount of energy, or heat, it takes to raise
the temperature of 1 gram of water by 1 degree Celsius (1.8 degrees
Fahrenheit). One calorie is equal to 4.184 joules, a common unit of energy
used in the physical sciences.
Most of us think of calories in relation to things we eat and drink, as in
"This can of soda has 200 calories." It turns out that the calories listed
on a food package are actually kilocalories (1000 calories = 1
kilocalorie). So that can of soda actually has 200,000 calories (but don't
worry, the same applies to exercise -- when an exercise chart
Food energy - Wikipedia, the free encyclopedia
** Food energy **
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*Food energy* is energy that animals (including human beings) derive from
their food, through the process of cellular respiration, the process of
joining oxygen with the molecules of food (aerobic respiration) or of
reorganizing the atoms within the molecules for anaerobic respiration.
Animals need a minimum intake of food energy in order to sustain their
metabolism and drive their muscles. For humans, food energy typically comes
from joining oxygen with carbohydrates, fats, proteins, organic acids,
polyols, and ethanol present in the diet.^ Some diet components that
provide little or no food energy, such as water, minerals, vitamins and
fiber, may still be necessary to health and survival for other reasons.
Ruminants are able to extract food energy from the respiration of cellulose
thanks to bacteria in their rumens.
In the International System of Units, energy is measured in joules (J) or
its multiples; the kilojoule (kJ) is most often used for food-related
quantities. An older metric system unit of energy, still widely used in
food-related contexts, is the calorie; more precisely, the "food calorie",
"large calorie" or kilocalorie (kcal or Cal), equal to 4.184 kilojoules.
(It should not be confused with the "small calorie" (cal) that is often
used in chemistry and physics, equal to 1/1000 of a food calorie.) Within
the European Union, both the kilocalorie ("kcal") and kilojoule ("kJ")
appear on nutrition labels. In many countries, only one of the units is
displayed; in the US and Canada the unit is spelled out as "calorie" or
Fats and ethanol have the greatest amount of food energy per mass, 38 and
30 kJ/g (9 and 7 kcal/g), respectively. Proteins and most carbohydrates
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